Hemodynamics in the pulmonary arterial, capillary and venous beds will be investigated with experiments and mathematical modeling. In the experimental study an excised lung lobe will be placed in an airtight chamber for static and dynamic measurements. When the alveolar pressure is raised above the arterial pressure, the pulmonary capillary bed will be collapsed, allowing separate measurement of arterial and venous compliances. From the subsequent measurement of the total compliance, the capillary can be determined. By perfusing the lung both in forward and backward directions, capillary pressure as well as arterial and venous resistances may be determined from the change in volume of the vascular bed and the known compliances. Alterations in these hemodynamic parameters caused by edema, embolism, hypoxia, and vasoactive substances will be quantitatively documented. Sites of action of the intervention may be inferred from the longitudinal distribution of resistances. Correlations of capillary pressure with severity of edema, embolism and dosage of vasoactive agents will be attempted. A mathematical model incorporating the arterial, capillary and venous beds will be developed. Given alveolar pressure, chamber pressure, outlet pressure and flow rate, pressure-flow relations of the arterial, capillary and venous beds may each be determined. Some of the basic physical parameters used in the model will be furnished by the experiments; through a parametric study, the model will elucidate the interrelationship of the various parameters. New experiments are also expected to emerge from this mutual feedback of experiments and mathematical modeling.